The objective of the CEOS/IVOS WG4 was to compare the results of several methodologies making use of pseudo-invariant sites for vicarious calibration or for radiometric intercomparisons. The work of the WG4 is summarized in the hereafter report. The sensors considered in this work are spaceborne medium spatial resolution sensors with multi-spectral capabilities operating in the visible to thermal infrared. This intercomparison was carried out using a reference dataset which is also available from this page and is described in the same report.